userLikes.py

class Post(models.Model):

    user = models.ForeignKey(User, on_delete=models.CASCADE)
    description = models.CharField(max_length=1000)
    image = models.ImageField(null=True)
    
    '''
    https://docs.djangoproject.com/en/1.10/topics/db/examples/many_to_many/
    https://docs.djangoproject.com/en/dev/topics/db/queries/#backwards-related-objects
    http://stackoverflow.com/questions/2642613/what-is-related-name-used-for-in-django
    '''

    likes = models.ManyToManyField(User, through='PostComments', related_name="likes")
    shares = models.ManyToManyField(User, through='PostShares', related_name="shares")
    

    created_at = models.DateTimeField(auto_now_add=True)
    updated_at = models.DateTimeField(auto_now=True)


    def get_comment_count(self):
        return len(self.postcomments_set)

    def get_share_count(self):
        return len(self.postshares_set)

    def __str__(self):
        return self.description
        
class PostShares(models.Model):

    sharing_user = models.ForeignKey(User, on_delete=models.CASCADE)
    post = models.ForeignKey(Post, on_delete=models.CASCADE)

    created_at = models.DateTimeField(auto_now_add=True)
    updated_at = models.DateTimeField(auto_now=True)

class PostLikes(models.Model):

    liking_user = models.ForeignKey(User, on_delete=models.CASCADE)
    post = models.ForeignKey(Post, on_delete=models.CASCADE)

    created_at = models.DateTimeField(auto_now_add=True)
    updated_at = models.DateTimeField(auto_now=True)
    
    
'''
My View Starts
'''
def like_status(request):
	if request.method == "POST":
		post_id = request.POST.get('post_id')

		user = request.user
		post = get_object_or_404(Post, pk=post_id)

		post_likes = PostLikes(liking_user=user, post=post)
		
    How should I check if the like is already there and then remove it or add it
		'''
		if post.likes.filter(id=user.id).exists():
			post.likes.remove(user)
			message = "You unliked this"
		else:
			post.likes.add(user)
			message = "You liked this"
		'''
		ctx = {'likes_count': 10, 'message': message}
		return HttpResponse(json.dumps(ctx), content_type='application/json')